This exploratory project proposes to describe in some depth the structural changes families experience during the critical transitions which punctuate stages of development over the life span. Joining the concepts of two complementary theories, family development and family stress, to generate a stage-transitional model, the project operationalizes "critical transitions" by the "pile up" of developmental stressors to which families respond with structural transformations. The sampling design calls for three marital cohorts of twenty families each strategically selected to maximize the likelihood of experiencing developmental and nondevelopmental stressor events: a child bearing cohort (3-7 years married), a cohort with adolescents at home (13-17 years married) and a post-parental cohort (23-27 years married). Methods of data collection include semi-structured interviews for eliciting current and retrospective transitional experiences; and tests and instruments for assessing the frequency and severity of critical life events and the use of coping mechanisms. In this first exploratory phase, data analysis will focus on eliciting the range and modalities of family behavior characterizing the three marital cohorts studied. Initially, simple distributions of events will be examined and compared across cohorts, such as the pile up of developmental and nondevelopmental stressors, the use of coping mechanisms, the thresholds of disorder experienced before moving into a critical transition, the time required to achieve reorganization of the family's role structure. More formal comparison of cohorts on such dimensions will be undertaken via analysis of variance where appropriate but due to small sample size must be considered exploratory rather than definitive tests of hypotheses.